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- Maria Frieden Abbey or Dahlem Abbey (Abtei Maria Frieden), Dahlem: Trappist nuns 1952-today
- Mariawald Abbey (Abtei Mariawald), Heimbach: Cistercian monks 1480-1795, Trappists 1862-today
- Marienbaum Abbey (St. Mariä Himmelfahrt, Marienbaum or Birgittenkloster Marienbaum), Xanten: Brigittine double monastery 1460-1802
- Marienborn Abbey (Kloster Marienborn), Burbach, Hürth: Cistercian nuns 1233-1802
- Marienborn Priory (Kloster Marienborn), Lütgendortmund: Beguines (dates tbe)
- Marienfeld Abbey (Kloster Marienfeld), Harsewinkel: Cistercian monks 1185-1803; Benedictine monks 2004-today
- Marienhof Priory or Abbey (Kloster Marienhof), Hamm: Cistercian nuns 1270-1290 (moved to Kentrop)
- Marienmünster Abbey (Abtei Marienmünster), Marienmünster: Benedictine monks 1128-1803; Passionists 1965-today
- Marienthal Priory or Marienthal Carmel, formerly Marienthal Abbey (Kloster Marienthal), Hamminkeln: Augustinian Hermits 1258-1806, Carmelites 1986-today
- Marsberg:
- Marsberg Friary (Kapuzinerkloster Marsberg), Niedermarsberg: Capuchin Friars 1745–1812
- Obermarsberg Abbey (Kloster Obermarsberg), Obermarsberg: Benedictine monks, 8th century – 1803
- Merten Priory (Kloster Merten), Merten, Eitorf: Augustinian Hermits (female) 1160-1802
- Meschede Abbey (Stift Meschede), Meschede: secular canonesses 870-1310; canons 1310-1805
- Metelen Abbey (Stift or Kloster Metelen), Metelen: nuns (order unknown) 889-C13; canonesses (secular or regular, but Augustinian for some of the time) 13th century-late 15th century; women's collegiate foundation (Damenstift) late 15th century-1803
- Michaelsberg Abbey (Abtei Michaelsberg), Siegburg: Benedictine monks 1064-1803, 1914-today
- St. Maurice's Abbey, Minden (Kloster Sankt Mauritius, Minden), Minden: tbe
- Mönchengladbach:
- Mönchengladbach Abbey (Abtei Mönchengladbach or Rathaus Abtei): Benedictine monks 1663-1802
- Neuwerk Priory (Kloster Neuwerk), Neuwerk, Mönchengladbach: anchorites 1133-1250; Benedictine nuns 1250-1802; Salvatorian Sisters 1879-1889; Lüdinghauser Franciscan Sisters 1889-1961; Salvatorian Sisters 1961-today
- St. Francis' House, or Franciscan Hospital (Franziskushaus): hospital of the Franciscan Sisters of the Atonement and the Love of Christ (dates tbe)
- Mörmter Friary (Kloster Mörmter), Mörmter: Franciscan friars, 1922-today
- Mülheim Commandery, later Mülheim Priory or Friary (Deutschordenskommende Mülheim), Mülheim, Warstein: Teutonic Knights 1266-1809; Olpe Sisters 1885-1994; "Community of the Blessed Declarations", 1995-today
- Münster:
- Alexian Hospital, Münster (Alexianer-Krankenhaus Münster), Münster: Alexians (date tbe)-today
- St. Ludger's Abbey or Priory, Münster (Stift St. Ludgeri, Münster): collegiate foundation 1173-1811
- St. Martin's Abbey or Priory, Münster (Stift St. Martini, Münster): collegiate foundation 1187-1811
- St. Maurice's Abbey or Priory, Münster (Stift St. Mauritz, Münster): collegiate foundation, after 1064-1811
Read more about this topic: List Of Christian Religious Houses In North Rhine-Westphalia